responses of terrestrial ecosystems to drought
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Responses of terrestrial ecosystems to drought. 肖劲锋 Earth Systems Research Center, University of New Hampshire. The 7th International Symposium on Modern Ecology Guangzhou, China, June 10-12, 2013. Where are New Hampshire and UNH?. Where are New Hampshire and UNH?. - PowerPoint PPT PresentationTRANSCRIPT
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Responses of terrestrial ecosystems to drought
肖劲锋Earth Systems Research Center, University of New Hampshire
The 7th International Symposium on Modern EcologyGuangzhou, China, June 10-12, 2013
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Where are New Hampshire and UNH?
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Where are New Hampshire and UNH?
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• “a significant deviation from the normal hydrological conditions of an area” – Palmer 1965
• “drought means a sustained, extended deficiency in precipitation” - The World Meteorological Organization (WMO 1986)
• “drought means the naturally occurring phenomenon that exists when precipitation has been significantly below normal recorded levels, causing serious hydrological imbalances that adversely affect land resource production systems” - The UN Convention to Combat Drought and Desertification (UN Secretariat General 1994)
• “the percentage of years when crops fail from the lack of moisture” – FAO 1983
Definitions of drought
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Figure 3.1 Figure 10.4
Global climate change
Source: IPCC, AR4, Nov 20075
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Trend maps in annual PDSI
Dai, JGR, 2011
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Dai, JGR, 2011
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Carbon release
Carbon uptake
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1. Remote sensing
2. Ecosystem modeling
3. In-situ data and upscaling
Case studies
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Zhang et al., ERL, 2012
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Zhang et al., ERL, 2012
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Zhang et al., ERL, 2012
• The drought reduced regional annual GPP and NPP in 2010 by 65 and 46 Tg C yr−1, respectively. Both annual GPP and NPP in 2010 were the lowest over the period 2000–2010
• The negative effects of the drought were partly offset by the high productivity in August and September and the farming practices adopted
• Like summer droughts, spring droughts can also have significant impacts on vegetation productivity and terrestrial carbon cycling
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1. Remote sensing
2. Ecosystem modeling
3. In-situ data and upscaling
Case studies
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• A process-based biogeochemical model, the Terrestrial Ecosystem Model (TEM)
• TEM simulates the cycling of carbon, nitrogen, and water among vegetation, soils, and the atmosphere at monthly time steps.
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Mild
Moderate
Severe
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Tree-ring chronologies
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• Most droughts generally reduced NPP and NEP in large parts of drought-affected areas.
• Out of the seven droughts, three (1920–30, 1965–68, and 1978–80) caused the countrywide terrestrial ecosystems to switch from a carbon sink to a source, and one (1960–63) substantially reduced the magnitude of the countrywide terrestrial carbon sink.
• Strong decreases in NPP were mainly responsible for the anomalies in annual NEP during these drought periods.
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1. Remote sensing
2. Ecosystem modeling
3. In-situ data and upscaling
Case studies
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23SOO (CA)UMBS (MI) Fort Peck (MT) Mead Rotation (NE)
AmeriFlux, other regional flux networks, and FLUXNET
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Gridded flux fields
Eddy flux
Upscaling
MODIS data, climate data, and other spatial data
Conceptual framework for upscaling of fluxes from towers to broad regions
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EC-MOD upscaling system
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Upscaling AmeriFlux data to the national scale
Xiao et al., Agri. For. Met., 2008; Remote Sens. Environ., 2010; Agri. For. Met., 2011
• Observations from 42 towers
• Data-driven approach
• MODIS data streams
• Gridded EC-MOD flux dataset
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GPP NEE
GPP NEE
2006 2006
2009 2009
Xiao et al. unpublished
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GPP NEE
ER ET
Global flux fields – EC-MOD (2000-2010)
Xiao et al. unpublished
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2002
ET
NEEGPP
PDSI
Xiao et al. unpublished
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2005
ET
NEEGPP
PDSI
Xiao et al. unpublished
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GPP (South America) NEE (South America) ET (South America)
ET vs. GPP ET vs. NEE NEE (Globe)
Xiao et al. unpublished
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2007
2009
2010
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Indirect effects?
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Summary
• Drought has significant effects on plant growth and carbon fluxes
• Severe extended droughts could substantially reduce net carbon uptake or even lead to carbon sources
• Strong decreases in NPP were mainly responsible for the anomalies in annual NEP during drought periods
• The different methods are useful and complementary
• Future droughts will likely have larger positive feedbacks to the climate system
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Ongoing and future research
• Soil hydrology and respiration
• Tree mortality and fire
• Droughts vs. heat waves
• Uncertainty
• Food security
• Team effort
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• Soil hydrology and respiration
• Tree mortality and fire
• Droughts vs. heat waves
• Uncertainty
• Food security
• Team effort
Ongoing and future research
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• Soil hydrology and respiration
• Tree mortality and fire
• Droughts vs. heat waves
• Uncertainty
• Food security
• Team effort
Ongoing and future research
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• Soil hydrology and respiration
• Tree mortality and fire
• Droughts vs. heat waves
• Uncertainty
• Food security
• Team effort
Ongoing and future research
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• Soil hydrology and respiration
• Tree mortality and fire
• Droughts vs. heat waves
• Uncertainty
• Food security
• Team effortCourtesy of Changsheng Li
Ongoing and future research
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• Soil hydrology and respiration
• Tree mortality and fire
• Droughts vs. heat waves
• Uncertainty
• Food security
• Team effort
Ongoing and future research
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Special session at 2013 AGU meeting
B31: Impacts of Extreme Climate Events and Disturbances on Carbon DynamicsConvener(s): Jingfeng Xiao (University of New Hampshire) and Shuguang Liu (USGS EROS)
San Francisco, Dec 9-13, 2013Since 2011
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Dr. Jingfeng XiaoGlobal Ecology Group
Earth Systems Research CenterUniversity of New Hampshire
Email: [email protected]://globalecology.unh.edu
• Carbon cycle• Ecosystem modeling• Remote sensing• Data assimilation• Data synthesis• Upscaling• Earth System Models